Lubricating oil for jet engines



United States Patent 3,121,061 LUBRIQATING OIL FOR JET ENGINES John D. Bartleson, Franklin, Mich, and Robert B. Faris,

.1r., Solon, Ohio, assignors to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Filed Oct. 7, 1960, Ser. No. 61,091 4 Claims. ((31. 252-59) This invention relates to lubricating oils particularly adapted for low temperature use and to a method of making the same.

Lubricating oils which are to be used at low temperatures are subject to a number of stringent requirements including pour point and viscosity specifications which are dictated by the nature of their use. For example, many military airplanes are equipped with jet engines. The jet engines must be capable of starting easily in the cold temperatures of high altitudes. This means that jet engine lubricants are among those lubricants which must meet very rigid low temperature specifications in order to be acceptable. The manufacture of jet engine lubricants therefore presents special problems that are not encountered in the manufacture of lubricants for use at temperatures ordinarily encountered on the temperate parts of the earths surface.

The United States Air Force has established certain specifications for jet engine lubricants of varying types. These specifications in general are extremely diflicult to meet and a considerable amount of research and investigation has been performed in order to provide satisfactory lubricating compositions. One such specification for jet engine lubricating oil is grade No. 1005. According to the United States Air Force specifications, this grade of oil must have a kinematic viscosity of at least 5 centistokes at 100 F. and a pour point of 75 F. Additional specifications require a viscosity at --40 F. of not over 350 centistokes and also a flash point of not less than 225 F. Specifications such as these are very difficult to meet because, in general, oils which have such a low pour point usually have a kinematic viscosity at 100 F. lower than that demanded so that they are too thin to lubricate properly at this temperature. Converseiy, an oil which has a viscosity of at least 5 ceuti stokes at 100 F. in general has too high a pour point to meet the -75 F. specification. To meet the flash point specification, heavier components are needed, but these raise the viscosity at 40 F. and often raise the pour point. Attempts have been made to blend naturally occurring petroleum lubricating oils in order to meet the specifications. However, these attempts have not been successful because, when a low viscosity petroleum oil having a low pour point is blended with a higher viscosity petroleum oil having a relatively high pour point, the resultant blend, although it may have the low pour point desired, normally possesses too low a viscosity.

Various refining procedures, such as solvent refining, urea and thio urea adduction, and thermal diffusion, fail to give oils which would meet the specifications.

It is an object of this invention to provide a lubricating oil which satisfies the United States Air Force specifications for grade 1005 oil. It is a further object of the invention to provide a lubricating oil which is eminently suitable for use at low temperatures under a variety of external conditions. Other objects or" the invention will become apparent as the description of the invention proceeds.

It is known that a variety of polymer oils can be prepared utilizing olefins of relatively low molecular weight. Such oils may be produced by polymerizing olefins in the usual manner with the aid of polymerization catalysts to obtain oil-like polymers having lubricating properties,

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2 and usually in the preparation of such polymer oils the crude polymer is fractionally distilled to produce fractions having different boiling points and varying properties.

The lubricating oils of this invention are blends of two or more polypropylene fractions, one of which boils in the kerosine boiling range, i.e., 329 F. to 368.6 F. (760 mm.) and has a viscosity of within the range of 2.58 to 4.05 centistokes at 100 F. and the other of which boils in the gas oil boiling range, i.e. 368.6 F. to 475.7 F. (760 mm.) and has a viscosity within the range of 7.8 to 17.3 centistokes at 100 F. Neither one of these fractions alone meets the specification for grade 1005 lubricating oil. The kerosine fraction has the low pour point that is required, but, as might be expected, its kinematic viscosity is too low to meet the specification, and it fails to meet the flash point specification. On the other hand, the gas oil fraction meets the viscosity specification but has far too high a pour point to be satisfactory. Surprisingly, we have found in accordance with the present invention that a blend within the range of from 30.2 to 47% of the kerosine fraction with from 53 to 69.8% of the gas oil fraction, meets all the requirements of the pour point, kinematic viscosity, and flash point of the above stated military specification. This result is unobvious because as indicated hereinabove the same results cannot be achieved by the comparable blending of two naturally occurring petroleum fractions. Furthermore, producing a synthetic oil from a raw propylene polymer having a boiling range from 329 F. to 475.7 P. which would correspond to the initial boiling point of the kerosine fraction and the final boiling point of the gas oil fraction also does not meet the criteria of this specification. It is neces sary, therefore, in order to meet the criteria of this specification, to separate the specific fractions from a polypropylene polymer and re-blend these fractions in proportions in which they do not naturally occur.

The synthetic oils of the invention may be prepared by blending heavier and lighter fractions from a raw propylene polymer in specific proportions. Thus, for example, a synthetic oil according to the invention may be prepared by blending a polypropylene gas oil fraction with a polypropylene kerosine fraction, each fraction having been obtained by distillation from a crude propylene polymer. The kerosine fraction of the blend is a fraction having a boiling range of 329 'F. to 368.6 F., having a viscosity of 2.58 to 4.05 centistokes at 100 F. and the gas oil fraction of the blend is a fraction having a boiling range of 368.6 F. to 475.7 F. and having a viscosity of 7.8 to 17.3 centistokes at 100 F. Such fractions are obtained by the fractional distillation of the crude product resulting from the catalytic polymerization of propylene. For the oil compositions of the invention, the percentage by weight of each fraction in the blend may range from 30.2 to 47% of the kerosinc fraction and 53 to 69.8% of the gas oil fraction.

This invention will be further illustrated by references to the following specific examples.

EXAMPLE A A polypropylene was prepared by the polymerization of propylene at 33 F. using a propane diluent, H promoter, and p.s.i.g. BF The procedure was as follows:

Fourteen grams of technical sulfuric acid were placed in a bomb which has been previously cleaned and flushed with nitrogen, and 685 grams of propylene (75% pure) were then added. Cold water was circulated through the jacket of the bomb and the agitator was started. The propylene pressure was 50 p.s.i.g. It was intended to add BF to a total pressure of 400 p.s.i.g., but as the BF was added and the total pressure reached 100 p.s.i.g., a violent reaction took place, as evidenced by a rapid increase in pressure. The BF supply was immediately shut off and when the pressure in the bomb reached 500 p.s.i.g. the bomb was vented. The pressure dropped rapidly and remained constant when it reached 80 p.s.i.g. The reaction required 5 minutes, but to insure complete polymerization the reaction was continued for one hour. At the end of this time the contents of the bomb were pressured out and the oil was placed in a beaker with sodium hydroxide present in order to neutralize the acid and BF The raw polymer was allowed to stand overnight and was then heated in a steam bath for two hours and filtered. Pentane was used to wash the caustic out of the raw polymer and the pentane was then evaporated in the steam bath.

Three hundred fifty grams of the raw polymer were obtained from the after-treatment and 238 grams of acid free raw polymer remained at the conclusion of the after-treatment. The acid free raw polymer was then distilled from sodium carbonate to a pot temperature of 490 F. (overhead temperature of 329 F.). Thirteen grams of gasoline boiling range polymer were removed by this treatment and a residue of 225 grams of polymer oil was obtained. The polymer oil was then filtered preparatory to vacuum distillation and had the following constants:

Vis. at 100 F cstks 13.25 Vis. at 210 F cstks 3.12 V1 107 One hundred eighty-seven and seven-tenths grams of the above product were vacuum distilled at mm. pressure in the presence of sodium carbonate in order to prevent decomposition. Sixty and seven-tenths grams of gas oil fraction (30-0.2395.6 F./l0 mm., equivalent to 368.6 F.475.7 F./760 mm.) were collected.

EXAMPLE B A polypropylene was prepared by the polymerization of propylene as follows:

Fourteen grams of technical sulfuric acid were placed in a bomb which had been previously cleaned and flushed with nitrogen, and 770 grams of propylene (75% pure) were added. The pressure in the bomb was 70 p.s.i.g. with cold water (40 F.) circulating in the jacket. Hydrogen was added to a pressure of 370 p.s.i.g. and the agitator was started. It was intended to add BF to 570 p.s.i.g., but when the pressure reached 500 p.s.i.g. a reaction took place with the pressure rising to 700 p.s.i.g. and the temperature to 140 F. The temperature and pressure dropped slowly over a period of 10 minutes until the temperature was again 40 F. and the pressure was 300 p.s.i.g. The reaction was continued for one hour. The excess pressure was then vented, and the contents of the bomb were pressured into a stainless steel pail. The oil was then decanted into a 2-liter beaker witht sodium hydroxide flakes present to neutralize the acid and BF The oil was allowed to stand overnight. Three hundred one grams of oil and catalyst complex were recovered, and the oil and sodium hydroxide were then heated in a steam bath for one hour, at the end of which time the oil was filtered. One hundred ninety-six grams of acid free raw polymer oil were distilled from sodium carbonate to a pot temperature of 490 F. (overhead temperature of 329 F.) and the polymer oil was then filtered preparatory to vacuum distillation and had the following constants:

Vis. at 100 F ..cstks 13.92 Vis. at 210 F cstks 3.02 V.I. 69.0

One hundred sixty and nine-tenths grams of this prod- 45. not were vacuum distilled at 10 mm. pressure in the presence of sodium carbonate to prevent decomposition. Sixty-one and four-tenths grams of the gas oil fraction were collected.

EXAMPLE C A polypropylene was prepared by the polymerization of propylene as follows:

Fourteen grams of technical sulfuric acid were placed in a bomb which had been previously cleaned and flushed with nitrogen, and 766 grams of propylene (75 pure) were then added. The pressure of the propylene-propane mixture was 50 p.s.i.g. at 40 F. Hydrogen was then added until the total pressure was 550 p.s.i.g. It was intended to add BF to a total pressure of 750 p.s.i.g. but when the pressure reached 680 p.s.i.g. a reaction took place resulting in a rise in pressure to 960 p.s.i.g. and a rise in temperature to 240 F. Over a period of ten minutes the pressure dropped to 580 p.s.i.g. and the temperature to 40 F. The reaction was continued for one hour and at the end of this time the bomb was vented and the contents thereof were pressured into a stainless steel pail. Five hundred twenty grams of oil and catalyst complex were obtained. Four hundred fifty-four grams of oil were decanted into a beaker with sodium hydroxide present to neutralize the acid and B1 The oil was then placed in a steam bath and heated for two hours. At first the oil became a dark red with the evolution of dissolved hydrogen and B1 The oil then became a light yellow and was allowed to stand overnight.

The raw polymer oil was filtered and removed from the sodium hydroxide with pentane, the latter being evaporated in a steam bath. The acid free polymer oil was then distilled from sodium carbonate to a pot temperature of 490 F. (overhead temperature of 329 F.). Three hundred thirty-five and eight-tenths grams of the product of the distillation were vacuum distilled at 2 mm. pressure in the presence of sodium carbonate. Eighty-five and two-tenths grams of gas oil (233.6- 323.6 F./2 mm., equivalent to 368.6-475.7 F./760 mm.) were collected.

EXAMPLE D A polypropylene was prepared by the polymerization of propylene as follows:

Fourteen grams of technical sulfuric acid were placed in a bomb which had been previously cleaned and flushed with nitrogen, and 826 grams of propylene (75 pure) were then added. Cold water at 40 F. was circulated in the bomb jacket, the pressure of the propylene being 50 p.s.i.g. Hydrogen was added to a total pressure of p.s.i.g., and BF was then added to a pressure of 270 p.s.i.g. A reaction then took place resulting in a pressure rise to 640 p.s.i.g. and a temperature rise to 215 F. In about ten minutes the temperature had dropped to 40 F. and the pressure to p.s.i.g. The polymerization was continued for one hour and at the end of this time the bomb was vented and the contents were pressured into a stainless steel container. Four hundred sixty-three grams of oil and catalyst complex were obtained. The oil was then decanted into a beaker with sodium hydroxide present to neutralize the BF The raw polymer oil was then allowed to stand overnight, and was then heated in a steam bath for two hours, filtered, and extracted from the caustic with pentane, the latter being evaporated in the steam bath. Four hundred grams of the acid free polymer oil were distilled at atmospheric pressure at a pot temperature of 490 F. (overhead temperature of 329 F.) in the presence of sodium carbonate to prevent decomposition. Three hundred thirty-five and eight-tenths grams of polymer oil were vacuum distilled at a pressure of 2 mm. in the presence of sodium carbonate.

grams of gas oil were recovered.

One hundred six and six-tenths EXAMPLE E A polypropylene was prepared by the polymerization of propylene as follows:

Fourteen grams of technical sulfuric acid were placed in a clean bomb and 716 grams of propylene (75% pure) were then added. The pressure at 33 F. was 70 p.s.i.g. Hydrogen was then added to a total pressure of 120 p.s.i.g. and BF was then added to a pressure of 170 p.s.i.g. After 75 minutes the reaction was assumed to be complete and the bomb was vented and flushed with nitrogen. Eight hundred ten grams of a methanol solution of sodium hydroxide were then added to neutralize the BR; and sulfuric acid. The bomb was then Two hundred eleven and eight-tenths grams of polymer oil were vacuum distilled at a pressure of 2 mm. of mercury in the presence of sodium carbonate and 64.7 grams of gas oil were collected.

Although the foregoing examples have specifically disclosed the preparation of the gas oil fractions only, it is, of course, obvious that the kerosine fractions are attained by recovering lower boiling fractions in the distillation of the product in each case. These latter fractions were recovered from the corresponding raw polymers over a boiling range of from 329 F. to 368.6 F. (760 mm.).

The above fractions were blended as indicated in the following table with the results shown.

Table I Fractions Percent by Kerosine Gas Oil" Gas Oil Blend Blend Blend Blend Example No. From Weight Viscosity Viscosity Pour Pour Flash Viscosity Viscosity Example Kerosine 100 F. 100 F. Point, Point, Point, 100 F. 210 F. No. in Blend (cstks) (cstks) F. F. (cstks) (estks) 1 Calculated. 2 Not measured. 3 Polyethylene fraction heated with steam to 320 F. at a pressure of 200 p.s.i.g. for minutes. The bomb was then cooled and the contents thereof were pressured into a stainless steel pail. Thirteen hundred thirty grams of material were obtained of which 520 grams were raw polymer oil. The yield was 96.8%. The raw polymer oil was then filtered and washed with water to remove methanol and sodium hydroxide, the washing being continued until the water tested neutral to pH paper. The acid free polymer oil was dried and filtered and 440 grams of polymer oil were obtained. The yield was 82%. Seventy-five and twotenths grams of gas oil were collected.

EXAMPLE F A polypropylene was prepared by the polymerization of propylene as follows:

Six hundred milliliters of pentane were charged to a bomb which had previously been cleaned and flushed with nitrogen. A slurry of 3.5 grams of sodium chloride (1.15 mole percent based on propylene) and pentane was added, and then 8.15 grams (1.15 mole percent) of technical sulfuric acid were added. Four hundred five grams of propylene (75% pure) were added and cold water was circulated through the bomb jacket. The pressure of the propylene was 80 p.s.i.g. but when the bomb agitator was started the pressure dropped to 50 p.s.i.g. Boron trifiuoride was then introduced to a total pressure of 150 p.s.i.g. For the first hour the pressure remained constant but during the second hour of the reaction the pressure dropped slowly to 120 p.s.i.g. After two hours the bomb was vented and the pentane solution was removed from the bottom of the bomb. It was then placed in two l-liter beakers with sodium hydrom'de present to neutralize the BF and acid. The solution was allowed to stand for two days, and 286 grams of oil were obtained with a yield of 94.2%. Two hundred forty-five grams of acid free polymer oil were distilled from sodium carbonate to a pot temperature of 490 F. (an overhead temperature of 329 F.) and the polymer oil was then filtered preparatory to vacuum distillation and had the following constants:

Vis. at 100 F cstks 4.91 Vis. at 210 F cstks 1.63 V.I. 89

From the above data it will be seen that Example No. 6 meets all of the specifications as to pour point, viscosity at F., and flash point. Extrapolation of the viscosity of 100 F. and 210 F. of the poor point shows it to meet the viscosity at -40 F.

Example 5 meets the specifications on viscosity but fails to meet the specification on flash point. It will be noted that this example contains a relatively high proportion of the kerosine component.

The flash points of Examples 1, 2, 3 and 4 were not measured, and it is believed likely that these examples would fail on flash point because they contain larger amounts of the kerosine component than Example 5, even though these examples meet the pour point and viscosity at 100 F.

Example 10 utilizes polyethylene oil in a kerosine fraction instead of polypropylene. Such a mixture meets specifications for pour point, viscosity at 100 F. and -40 F. but fails miserably on flash point.

By setting up regression equations embodying all of the above data, it is possible to calculate the extremes of proportions of the kerosine and gas oil components and their respective viscosities which will meet the pour point, flash point, and viscosity specifications, and these calculations are included as Examples 7, 8, and 9.

This application is a continuation-in-part of application Serial No. 596,818, filed July 10, #1956 and now abandoned.

We claim:

1. A lubricating oil for use at low temperatures consisting essentially of a blend of (1) an amount within the range of 30.2 to 47% of a polypropylene fraction having a boiling range of 329 F. to 368.6 F. and having a. viscosity at 100 F. within the range of 2.58 to 4.05 centistokes, and (2) an amount within the range of 53 to 69.8% of a polypropylene fraction having a boiling range of 368.6 F. to 475.7 F. and a viscosity within the range of 7.8 to 17.3 centistokes at 100 and a pour point of above 75 -F., producing a blend having a kinematic viscosity at 100 F. in excess of 5 centistokes, a pour point lower than -75 F., and a flash point in excess of 225 F.

2. A lubricating oil for use at low temperatures con sisting essentially of a blend of (1) 32% of a polypropylene fraction having a boiling range of 329 F. to 368.6 F. and having a viscosity at 100 F. of 2.58 centistokes, and (2) 68% of a polypropylene fraction having a boiling range of 368.6 F. to 457.7 F. and a viscosity of 7.8 centistokes at 100 F. and a pour point of about -75 F, producing a blend having a kinematic viscosity of 100 F. of 5.03 centistokes, a pour point lower than 100 F., and a flash point of 235 F.

3. A process of preparing a lubricating oil for use at low temperatures consisting essentially of the steps of fractionating a mixture of propylene polymers to obtain a first fraction having a boiling range of 329 to 368.6 F. and having a viscosity at 100 F. within the range of 2.5 8 to 4.05 centistokes, fractionating a mixture of propyl ene polymers to obtain a second fraction having a boiling range of 368.6 F. to 475.7 F. and having a viscosity Within the range of 7.8 to 17.3 centistokes at 100 F. and a pour point of above 75 F mixing an amount of said first fraction within the range of 30.2 to 47% with an amount of said second fraction within the range of 53 to 69.8% to produce a blend having a kinematic viscosity at 100 F. in excess of 5 centistokes, a pour point lower than -75 F. and a flash point in excess of 225 F.

4. A process of preparing a lubricating oil for use at low temperatures consisting essentially of the steps of fractionating a mixture of propylene polymers to obtain a 8 first fraction having a boiling range of 329 F. to 368.6 F. and having a viscosity at 100 F. of 2.58 centistokes, fractionating a mixture of propylene polymers to obtain a second fraction having a boiling range of 368.6 F. to

References Cited in the file of this patent UNITED STATES PATENTS 2,304,874 Barnard Dec. 15, 1942 2,329,714 Grasshof Sept. 21, 1943 2,508,744 Carlson et a1 May 23, 1950 2,525,788 Fontana et al Oct. 17,1 950 2,670,392 Glassmire et a1 Feb. 23, 1954 OTHER REFERENCES Kalichevsky et al.: Chemical Refining of Petroleum, Reinhold Pub. Corp. New York, 1942, page 413.

Georgi: Motor Oils and Engine Lubrication, Reinhold Pub. Corp., 1950, page 220 pertinent.

Lubrication of Industrial and Marine Machinery, 2d ed., 1954, Forbes-Wiley, pages .19 and 21 pertinent.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 121,061 February ll 19 4 John D. Bartleson et a1.

It is hereby certified that error appears in vthe above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 7, line 5, for "about" read above line 6, for "of", first occurrence, read at --a Signed and sealed this 4th day of August 1964 (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Commissioner of Patents Attesting Officer 

1. A LUBRICATING OIL FOR USE AT LOW TEMPERATURES CONSISTING ESSENTIALLY OF A BLEND OF (1) AN AMOUNT WITHIN THE RANGE OF 30.2 TO 47% OF A POLYPROPYLENE FRACTION HAVING A BOILING RANGE OF 329*F. TO 368.6*F. AND HAVING A VISCOSITY AT 100*F. WITHIN THE RANGE OF 2.58 TO 4.05 CENTISTOKES, AND (2) AN AMOUNT WITHIN THE RANGE OF 53 TO 69.8% OF A POLYPROPYLENE FRACTION HAVING A BOILING RANGE OF 368.6*F. TO 475.7*F. AND A VISCOSITY WITHIN THE RANGE OF 7.8 TO 17.3 CENTISTOKES AT 100*F. AND A POUR POINT OF ABOVE -75*F., PRODUCING A BLEND HAVING A KINEMATIC VISCOSITY AT 100*F. IN EXCESS OF 5 CENTISTOKES, A POUR POINT LOWER THAN -75*F., AND A FLASH POINT IN EXCESS OF 225*F. 